Search results for " Paramagnetic resonance"
showing 10 items of 567 documents
ODEPR of indium colour centres in the X- irradiated storage phosphor KBr:In
1995
The results of measurements of the magnetic circular dichroism of the optical absorption (MCDA) and optically detected electron paramagnetic resonance (ODEPR) of X-irradiated KBr :In crystals are presented. The MCDA bands and ODEPR parameters of In°(1) centers and In 2+ centres have been measured. The mechanism of the energy storage in KBr :In crystals is found not to be simply the formation of correlated F centre-In 2+ centre pairs as was assumed previously. Considerable similarities to the storage phosphor BaFBr :Eu 2+ were found for the photostimulated emission and read-out properties.
EPR of radiation defects in LiBaF 3 crystals
2002
EPR spectra of LiBaF 3 crystals have been investigated after X-irradiation at RT. A spectrum consisting of approximately 35 nearly equidistant EPR lines has a strong angular dependence on the line intensities. The spectrum is caused by a hyperfine interaction (hfs) of a spin S=1/2 with neighbouring groups of nuclei. The observed large number of hfs lines required Li nuclei being in the first shell and fluorine nuclei in the more distant second shell. We analysed the spectrum in the F-centre model, taking reduced hfs values of the F-centre in LiF and found qualitative explanation of the number of hfs lines. The angular dependence of the line intensities could be explained by an anisotropy of…
ESR dosimeter material properties of phenols compound exposed to radiotherapeutic electron beams
2017
Abstract There is a need for a sensitive dosimeter using Electron Spin Resonance spectroscopy for use in medical applications, since non-destructive read-out and dose archival could be achieved with this method. This work reports a systematic ESR investigation of IRGANOX ® 1076 exposed to clinical electron beams produced by a LINAC used for radiation therapy treatments. Recently, dosimetric features of this material were investigated for irradiation with 6 0Co γ -photons and neutrons in both pellet and film shape and have been found promising thanks to their high efficiency of radiation-matter energy transfer and radical stability at room temperature. Here the analysis of the dosimetric fea…
ESR response of phenol compounds for dosimetry of gamma photon beams
2014
Abstract In the present paper we investigate the features of IRGANOX® 1076 phenols as a material for electron spin resonance (ESR) dosimetry. We experimentally analyzed the ESR response of pellets of IRGANOX® 1076 phenols irradiated with 60Co photons. The best experimental parameters (modulation amplitude and microwave power) for dosimetric applications have been obtained. The dependence of ESR signal as function of γ dose is found to be linear in the dose range studied (12–60 Gy) and the lowest measurable dose is found to be of the order of 1 Gy. The signal after irradiation is very stable in the first thirty days. From the point of view of the tissue equivalence, these materials have mass…
ESR response of watch glasses to proton beams
2010
In this paper we have analyzed the electron spin resonance (ESR) signal of watch glasses irradiated with %60 MeV proton beams in the dose range between 1 and 105 Gy. The composition of samples expressed in oxides weight percentages has been obtained carrying out X-ray fluorescence spectrometry (XRF) mea- surements. The ESR signal has been studied in terms of its dependence on microwave power and modulation field in order to choose the optimal recording parameters. The dependence of the radioinduced signal on the exposure dose has been investigated. A numerical procedure aimed at improving the sensitivity in the low dose range has been developed.
The dynamics of the surface layer of lipid membranes doped by vanadium complex: computer modeling and EPR studies
2015
Abstract Penetration of the liposome membranes doped with vanadium complex formed in the liquid-crystalline phase from egg yolk lecithin (EYL) by the TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) spin probes has been investigated. The penetration process was followed by 360 hours at 24°C, using the electron spin resonance (EPR) method. The spectroscopic parameter of the partition (F) of this probe indicated that a maximum rigidity of the membrane was at 3% concentration of the vanadium complex. Computer simulations showed that the increase in the rigidity of the membrane corresponds to the closure of gaps in the surface layer of the membrane, and indicates the essential role of the membrane …
Hydrogen-related radiation defects in SiO2-based glasses
2008
Abstract Spectroscopic properties of hydrogen atom trapped in an oxygen vacancy in SiO2 glass were studied. Samples were loaded with D2 and H2 gases to convert O vacancies to pairs of Si–D and Si–H groups, and subsequently irradiated by F2 laser in order to destroy some of these groups. Electron paramagnetic resonance, infrared absorption and visible/UV absorption spectra were measured. Proton hyperfine doublet with splitting of 1.05 mT was found in all H2-treated/irradiated samples. UV-bleaching treatment showed that this signal is independent of the other, well-known hydrogen-related signals in silica. The size of the hyperfine splitting corresponds to twice the 1H nuclear Zeeman splittin…
Irradiation induced defects in fluorine doped silica
2008
International audience; The role of fluorine doping in the response to UV pulsed laser and c radiation of silica preforms and fibers was studied using electron spin resonance (ESR) spectroscopy. Exposure to radiation mainly generates E0 centers, with the same effectiveness in fibers and in preforms. The E'concentration in F-doped silica fibers is found to increase with UV energy fluence till a saturation value, consistently with a precursor conversion process. These results show the fluorine role in reducing the strained Si–O bonds thus improving the radiation hardness of silica, also after drawing process.
EPR hyperfine structure of the Mo‐related defect in CdWO 4
2005
The hyperfine structure (hf) of the electron paramagnetic resonance (EPR) spectrum of Mo-related impurity defects in CdWO4 crystals observed previously (U. Rogulis, Radiat. Meas. 29, 287 (1998) [1]) is reconsidered taking into account interactions with two different groups of neighbouring Cd nuclei. The best fit calculated EPR spectrum to the experimental is obtained considering 2 groups of 3 and 2 equivalent Cd nuclei, respectively. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of methemoglobin in human blood after ionising radiation by EPR
2015
In the present work presents results of investigations of radiation influence on blood of patients examined by radio-isotopes diagnosis (Tc 99m ), blood of Chernobyl clean-up workers and human blood irradiated by LINAC using Electron Paramagnetic Resonance (EPR). The EPR spectroscopy reveals information on electronic states of transition metal ions, particularly Fe 3+ in different spin states. It is shown that EPR spectra of blood of patients before examination has signal from metal-protein transferrin (g=4.3) and after administration of radio- isotope proves signal of Fe 3+ (methemaglobin) in the high spin state (g=6.0). The EPR spectra of Chernobyl liquidator display number of signals inc…